A raid boss that is immune to Intimidate may be Azumarill's greatest challenge yet, but we can still manage to push forward to victory in yet another 7 star Azumarill solo win and we don't even need to hit super effectively or have Taunt to do so. The timing on this clear is very tight which isn't helped by Decidueye's erratic move choices, and I even had to make a whole new Tera Fairy Sap Sipper Azumarill set for this one.
Azumarill runs Jolly with 28 Speed EVs to outspeed Decidueye, which allows it to avoid taking hits before debuffing and not get flinched. The rest of the EVs go into Attack (I have 248 here because of suboptimal vitamin order) and 238 Defense to maximize our bulk against Decidueye. Chilling Water is the key to survival, and I have it in the first slot instead of Mud-Slap because it ends up as the more consistent move to spam, especially when the raid randomly sets your cursor to slot 1. Reducing attack ends up more consistent than reducing accuracy here and having enough HP is important when we need to find time to set up, though one Mud-Slap for each phase is nice to reduce Decidueye's hit rates below 100. On my first attempt I tried Tickle, but the debuff cleanse + shield rendered that a poor approach, and so Chilling Water was my best bet to reduce its attack afterwards. Another option was Defense Curl, but it is more vulnerable to high damage ranges on +3 crits rather than directly lowering Attack, and is longer to set up after a death compared to Chilling Water being able to be done on my first life.
You may ask if Tera Poison/Flying Tera Blast would deal more damage due to being super effective and having no miss chance, and the answer is yes. I only thought of it after many iterations of the current strategy, and by then I thought that Play Rough still had a path to victory so it was just a matter of convenience and also using a natural tera type. I will give Play Rough some credit for having a chance to lower Attack, which may make a difference when there's very little time to properly set up Mud-Slap and Chilling Water at times.
This clear took many attempts and I actually had to sleep on it to figure out how to make enough time to win. Over many iterations of this battle I have come up with a fairly set turn-by-turn strategy for Azumarill's victory, and now I will detail my findings about how to handle this raid with Azumarill. Note that I will add some visuals, but they are mostly from various other failed runs since I didn't take many pictures of this winning attempt until the end so HP and time may be inconsistent.
Part 0: Resetting for AI
Getting a solid AI group is important. I found that dealing with Bulk Up's defense boost alone is just too slow to deal meaningful damage, so I need an AI that can lower Defense in the early phases which basically comes down to Weavile and Arcanine with Leer. In the end I decided to reset to lock in some AI and got Weavile first. I feel like both of these are pretty interchangeable, but Weavile can randomly freeze while Arcanine can randomly burn which may arguably be better for survivability.
Sometimes Weavile freezes were a thing, but with Decidueye getting double actions around half its HP, that's 8 chances for it to thaw out on a turn which is not very reliable to keep it stopped. I did actually get a freeze in my winning attempt, but it was on the turn I broke shield anyway so it didn't even get to move afterwards, and it thawed out on the AI's turn (I think the turn order made it so I broke the shield and the AIs got a turn of stun for that, and the next turn Decidueye was lastly stunned for me and it could hit the AI moving afterwards) so it didn't actually help me.
(The peak of AI chip damage before the shield that I have seen.)
The other AI I got were Heracross and Dudunsparce, and this was actually pretty important. Despite all the weaknesses on this team, it doesn't really matter because the AI naturally outspeeds so they can move before dying, and the AI has no respawn timers so it doesn't really matter if they die. Heracross likes to spam Megahorn and combined with Weavile's Leers, this can cause a lot of chip damage that can make a real difference when damage is the main bottleneck of the run (though the above screenshot got Decidueye to double action range too early and failed).
I found it worth resetting to get the AI's chip damage at least around the letter "a" in Unrivaled before the shield, but sometimes I would get even farther. Dudunsparce can put up Glare which can help survivability but isn't totally necessary with all the other AI options that can help like Staraptor, Sylveon, Umbreon, Drifblim, maybe Bellibolt but it doesn't seem to prefer Discharge, and the HP threshold for the required setup pre-sheild is lax enough that it's not totally necessary.
Part 1: The Start Pre-Shield
This is where the raid starts in proper. Before the buff reset + Bulk Up action, I like to put up 1 Mud-Slap and 1 Chilling Water, though sometimes I mash into Chilling Water first. Mud-Slap adding a miss chance is appreciated but not something we can afford to invest multiple turns in, so I only hit 1 in this phase. After the Bulk Up turn, I spam Chilling Water for consistency and usually get 3 turns of actions in this part, which is where most of the AI's chip damage will come into play, so it's important to actually attack here instead of stalling the timer. Bulk Up can be stopped by Dudunsparce's Glare which is occasionally helpful.
I feel like Decidueye usually picks randomly in this part and sometimes it doesn't find out I have Sap Sipper for the first 2 turns, and so when it resets my ability it may accidentally manage to hit Leaf Blade on the same turn, which confused me for a bit. Otherwise usually its AI chooses not to Leaf Blade after Sap Sipper is discovered, and afterwards it only chooses it on the turn after the ability reset wears off which is too late. With ideally 2 Leaf Blade fails and chances of weak moves, Azumarill has a good chance of preserving enough HP for the next phases.
Part 1.5: Decidueye's Moves
Here we can talk about Decidueye's attacks and how they affect Azumarill, and its move choices feel fairly random, with a good chance of anything showing up even from Turn 1 when Sap Sipper is unrevealed. Brave Bird is the strongest of the bunch by far, with Shadow Claw and Triple Arrows being weaker but having a solid crit chance. Leaf Blade usually leads to some free turns earlygame, and sometimes even it uses it as its double action in the endgame which is strange. The scripted Leaf Storm is irrelevant, but Grassy Terrain is actually a boon for us.
It is fortunate Decidueye is light on resets unlike the past few raids, but it's still a tough fight with its reset + Swords Dance + shield combo. As mentioned, Bulk Up is a major problem if left unchecked and the AI Leer is what makes this clear possible. The double actions start around above 50% HP, and so it's a delicate balance to chip Decidueye down enough in Phase 1 so that the battle is winnable, but not too far down that it starts doubling after Swords Dance.
Part 2: Shield and Sacrifice
After about 3 turns, Decidueye will reset its debuffs, put up a shield, and Swords Dance. Depending on timing you can sometimes sneak in Chilling Water between the debuff reset and Swords Dance going up but usually it doesn't happen. At this point Azumarill has to rely on some degenerate tactics from the Mewtwo solo strategies I found that may be a glitch, and I feared it might have been patched now that cheers showed up as durations, but fortunately it was not patched. The Mew video mentioned that dying while you have cheer duration up will
preserve the cheer effects infinitely after you respawn, and so I thought this could be a major factor for Azumarill's victory adding on 2 extra multipliers for the rest of the battle where it's needed most. The cheers don't show up on your status screen, but the difference is definitely felt and I confirmed with damage calcs on the defense cheer, as well as noting that I would heal about 70-80 with Shell Bell with the Attack cheer active.
My strategy for this section is to use Chilling Water, Defense Cheer, and Offense Cheer into death. Usually Azumarill only needs about above 50% of its HP to take 2 hits, and in this run I got critical Brave Birded to that point, but was still able to survive thanks to a merciful Shadow Claw pick. It is preferable to avoid any defense drops before this point as well.
Part 2.5: Death and Waiting
At this point you skip over some timer and trigger Decidueye into setting Grassy Terrain and Leaf Storming, or sometimes the other way around. Even if Azumarill is alive for this somehow, Leaf Storm is no threat and Grassy Terrain helps out a lot to get the last heals set up. Sometimes the countdown starts before Decidueye sets moves and sometimes it happens after everything which can be bad.
Part 3: Debuffs and Rebuffs
After respawning, this is when you set up debuffs and prepare to buff up with Belly Drum afterwards. In earlier attempts I tried to get greedy with Chilling Water and multiple Mud-Slaps, but I just did not have the turn count for it to work. I had to shave off some turns somehow and I was in the middle of refining the process in this winning attempt. I ended up deciding to just go for 1 Mud-Slap just to add the miss chance to possibly save animation time later on, and also going for only 1 Chilling Water to put its attack down to neutral. In previous runs I would try to get Decidueye to -1 Attack which would let me outpace 2 Brave Birds with Play Rough healing, but this was the only way I could think of to save a turn by taking a risk over being safe.
As I learned from the Delphox raid, taking less turns gives the AI less turns to RNG screw you, so I decided to settle for that and start buffing up. Grassy Terrain helps mitigate chip damage you take while setting everything and Belly Drumming, and after that you can start to spam Fairy tera Play Roughs until the end. Technically you could tera earlier to deal more shield chip damage but Mud-Slap and Chilling Water do so little anyway and I prefer to save the long animation until I know I'm in a viable position.
Part 4: Rough Play
At this point all you can do is spam Play Rough, and there is not much time left so you're lucky to get even 5, but somehow in this run I managed to sneak in up to 7 uses. The hardest part is actually breaking through the shield, because if you can break through then you basically get 2 free hits on him because of the stun turn, and then your AI status moves can actually pierce through and help out somewhat. There is really no other strategy to this point and it just relies on having enough time to click, as well as Azumarill not missing while Decidueye should miss for the least animation time wasted. I think it took about 4-5 Play Roughs to pierce the shield. Ideally Decidueye would just hit for weak Shadow Claws or Brave Birds that you can outpace with Shell Bell healing and some misses, but Triple Arrows defense drops can be a problem even this late into the run. It's also at this point that Decidueye randomly Leaf Bladed me on the second move sometimes and this was happening on a regular basis.
In this winning run it was down to the wire with the timer and I mashed Play Rough as fast I could, with my move cursor fortunately not resetting. After the HP warning you usually only have time for 1 turn, but sometimes you can sneak in 2 if animations are fast enough and the turn ends before the timer depletes. This is when I got the freeze from earlier that didn't help me since it wore off by the time I got to input this last turn anyway. Decidueye actually got 2 attacks on me posthumously and I think that's because the AI Weavile actually finished it with Ice Punch, so I didn't get a shot of the Decidueye fainted text on my end.
Part 5: Conclusion
I thought this was going to be very simple for Azumarill, but being immune to Intimidate made Decidueye much more of a problem than I was expecting on top of it setting up Attack buffs, so I was driven to some extremes but it was still barely winnable which I have to give Game Freak some credit for after Mewtwo. I'm still not a fan of the lowered timers lately which was the real bottleneck here, which made this very reliant on AI getting enough damage off in the start to get me through the rest of the way, which is something I didn't expect at all. You can see from my PP usage that I used about only 16 turns of PP, plus 2 cheers and the time spent dead, and this was a run that went down to the entire timer. Maybe if I remembered Toxapex had Chilling Water then the post-shield phase could be made smoother, but I was satisfied with this AI team.
EDIT:
I forgot to add this in, but here is a picture of Decidueye using Leaf Blade randomly near the end of the raid that I want to highlight.
